1. Field of the Invention
The present invention relates to a CCD (Charge Coupled Device) data pixel interpolation circuit and a digital still camera equipped with it, specifically to a CCD data pixel interpolation circuit which filters (thins out) data received from a CCD, interpolates the resulting data, and displays it on a display unit, and a digital still camera equipped with the interpolation circuit.
2. Description of the Related Art
A CCD is normally used for the image pickup device of a digital still camera. Image data captured by it is stored in a storage medium such as a compact flash memory or an IC memory card. To monitor the captured image, a display means such as an LCD (Liquid Crystal Display) is generally equipped in the digital still camera. In general, since the resolution of the display means such as an LCD is inferior to that of the CCD, pixel data captured by the CCD needs to be filtered (thinned out) and also interpolated.
FIG. 7 shows the configuration of the conventional CCD pixel interpolation circuit. A CCD 41 captures an image. Data from the CCD 41 is temporarily stored in a DRAM (Dynamic Random Access Memory) 43. An image processing control unit 42 reads in the data from the DRAM 43, performs a predetermined image processing, and writes the resulting data into a video memory 44. An LCD 45 displays the data stored in the video memory 44. A CCD controller 46 generates a pulse signal and other related signals to be used for reading data from the CCD 41. The CCD 41, the image processing control unit 42, the DRAM 43, and the video memory 44 are all connected to a main data bus 47.
The operation of pixel interpolation will then be explained with reference to FIG. 3 showing the configuration of the CCD. Either one of the primary color filters for R(Red), G(Green) and B(Blue) is attached on each pixel. A color signal corresponding to one of the colors R, G, and B is output from each pixel. Each line of data of the CCD 41 is read out. For example, pixels R11, G12, R13, G14, . . . in the first line are accessed in the order written. To obtain the red component value of the pixel B22, the average of the values of diagonally neighboring pixels R11, R13, R31, and R33 is calculated. The average is used to display an image of R22 on the LCD 45. Therefore, the average R22 cannot be calculated (in other words, a pixel interpolation of R22 cannot be made) until the value of pixel R33 in the next line has been read out. To make a pixel interpolation of the line including R22, three consecutive lines of pixel data have to be temporarily stored in a memory such as DRAM 43.
Furthermore, since CCD 41(see FIG. 7) cannot halt the pixel data capturing operation in general, the image processing control unit 42 must start a pixel interpolation operation after the CCD 41 has completed transmitting data. Therefore, it takes a long time to store all interpolated pixel data in the video memory 44 and also to display it on the LCD 45.
The aforementioned conventional CCD data pixel interpolation circuit has a problem that a large-scale memory such as a DRAM is needed to temporarily store pixel data.
Moreover, the pixel interpolation operation starts when all CCD pixel data is transmitted. Therefore, it takes a long time to store all the interpolated pixel data in the video memory and also to display it on the LCD.
It is an object of the present invention to provide a simple structured CCD pixel data interpolation circuit without a memory such as a DRAM which is used to temporarily store pixel data. The CCD pixel data interpolation circuit generates pixel data, which will be displayed on an LCD, at a high speed.
According to an aspect of the present invention, the CCD pixel data interpolation circuit filters(thins) out pixel data read out from the CCD, stores the filtered (thinned out) pixel data in a data buffer, reads out the stored pixel data from the data buffer, pixel-interpolates, and outputs the resulting pixel data to a display unit.
According to an aspect of the present invention, in the aforementioned CCD pixel data interpolation circuit, its pixel-interpolation operation is performed by weighting according to the distances from pixels used for the interpolation operation. According to an aspect of the present invention, the CCD pixel data interpolation circuit filters pixel data read out from a CCD, and stores the filtered (thinned out) pixel data in a video buffer, and pixel-interpolates the pixel data stored in the video memory.
According to an aspect of the present invention, a digital still camera comprises: a CCD, which captures an image; a display unit, which displays the pixel data obtained by subjecting the pixel data captured by the CCD to a predetermined operation; and a CCD pixel data interpolation circuit, which filters pixel data read out from the CCD, stores it in a data buffer, reads it out from the data buffer, pixel-interpolates using it, and outputs the resulting pixel data to a display unit, wherein the pixel-interpolating is done by weighting according to the distances from the filtered (thinned out) pixels used for pixel-interpolation.
According to an aspect of the present invention, a digital still camera comprises: a CCD, which captures an image; a display unit, which displays the pixel data obtained by subjecting the pixel data captured by the CCD to a given operation; and a CCD pixel data interpolation circuit, which filters the pixel data read out from the CCD; stores it in a video memory, reads it out from the data buffer, and pixel-interpolates using the pixel data stored in the video memory within the time period of outputting the filtered (thinned out) pixel data from the CCD.
According to an aspect of the present invention, the display unit in the aforementioned digital still camera is an LCD.